Environmental Science & Technology
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Item Soils Developed in Freshwater Marl Sediments in The Hagerstown (Great) Limestone Valley(1993) Shaw, Joey N.; Rabenhorst, Martin C.; Agronomy; Digital Repository at the University of Maryland; University of Maryland (College Park, MD)Certain calcareous soils occupying alluvial landscape positions in the Hagerstown (Great) limestone valley of western Maryland have developed from highly calcareous ( 60-100g/100g) marl sediments of Holocene age which range in depth from .5m to over 8m. These marlderived soils have a high pH ( 7. 5-8. 5) , low bulk density, and high porosity (0.5 to 0.6). The carbonate in the marl was developed from inorganic and biogenic processes. The marl was formed in now extinct ponds which had inundated alluvial landscape positions during parts of the Holocene period. Certain algae capable of accumulating carbonate internally and externally developed the majority of the marl. Pedogenic processes have transformed the marl sediments into highly calcareous Mollisols. The presence of buried surface horizons and coarse (> fine sand) carbonate forms render classification of these soils problematic. The coarse carbonate forms were mainly biogenic deposits, but these carbonates have been altered sufficiently by coating with pedogenic carbonate to identify calcic horizons. The drainage class is difficult to interpret as a result of the gleyed appearance of the marl sediments (chroma <3) and the high pH of these soils which inhibits Fe oxide reduction. Most of the marl-derived soils (70%) are better drained than the previous classification indicates. These soils have been mapped in the Great Valley in units named for the warners series (fine-silty, carbonatic, mesic Fluvaquentic Haplaquolls) and the Massenet ta series (fine-loamy, carbonatic, mesic, Fluvaquentic Hapludolls). However, proper classification may place these soils in the Typic Calciudolls subgroup. Some soils originally mapped in the very poorly drained Dunning units are very poorly drained marl-derived soils.Item Eutrophication, Hypoxia and Trophic Transfer Efficiency in Chesapeake Bay(2002) Hagy, James Dixon III; Boynton, Walter R.; Environmental Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Coastal eutrophication is a global problem that has contributed to loss of estuarine habitats and potentially decreased fisheries production. Hypoxia is often observed in eutrophic estuaries where it can be an important cause of habitat loss. This study utilized a suite of empirical analyses to examine key linkages relating coastal eutrophication to hypoxia, trophic structure, and trophic transfer efficiency in Chesapeake Bay (CB), USA. A salt- and water-balance model, or "box" model, was developed to quantify large-scale physical transport for CB, an input to many subsequent analyses. Historical ( 1950-1999) dissolved oxygen (DO) data for CB showed that moderate hypoxia (DO<2.0 mg1^-1) increased ~3-fold, modulated by spring river flow. Severe hypoxia (DO<0.7 mg1^1) occurred only in high flow years during 1950-1967, but was present annually since 1968. Analysis using tree-structured regression showed that hypoxia was the most important factor determining patterns of macrobenthic biomass in Chesapeake Bay. Carbon budgets showed that, where habitat quality was poor, macrobenthic biomass was much less than could be supported by the organic carbon supply. In these cases, even dramatic reductions in carbon supply would not be expected to limit benthic production and by extension, trophic transfers to upper trophic levels via the benthos. The effect of eutrophication and hypoxia on trophic structure and trophic transfer efficiency were examined by estimating trophic flow networks for three regions of CB during summer. In addition, a series of "rules" were described and used to infer the trophic flow network for a "restored" middle CB from historical data, comparative ecological relationships and mass balance constraints. Excessive carbon now through bacteria was the most pronounced symptom of eutrophication in the modern mid Bay. The microbial food web transferred organic matter to trophic levels comparable to large piscivorous predators, maintaining average trophic transfer efficiency, even as the fraction of primary production transferred to top predators decreased. In the restored Bay, increased macrobenthic production shifted metabolic activity away from the microbial food web, increasing the potential trophic transfer to fish by 7-fold, even as total primary production decreased to 63% of the current average.Item Pueraria lobata Willd. (Ohwi) kudxa: Limitations to Sexual Reproduction(1983) Abramovitz, Janet Naomi; Teramura, Alan H.; Botany; Digital Repository at the University of Maryland; University of Maryland (College Park, MD)The success of kudzu, Pueraria lobata Willd. (Ohwi), as a weedy invader in the southeastern United States is a result of its rapid growth rate, high leaf area index and ability to reproduce vegetatively. Populations at three sites near College Park, Maryland varied in their growth and reproduction, leaf area index, specific leaf weight, vine elongation rates, raceme density and seed production and dispersal. Soil characteristics, air temperature, humidity and photosynthetically active radiation (PAR) were measured at each site. The site which had the greatest vegetative productivity received significantly higher levels of PAR. Virtually no flowers or seeds were produced at the other two sites. At the site which produced a large number of flowers, successful sexual reproduction was limited by insufficient pollinator service during some periods of the season and low germination and seedling survivorship. Measurements of specific leaf weight, leaf area index, biomass, raceme production and seed set suggest that kudzu is a sun adapted plant. Even though it is capable of establishing itself in habitats of low or moderate irradiance, a greater ability for sexual reproduction was apparent in sun populations versus no sexual reproduction was apparent in sun populations versus no sexual reproductive success in populations occurring in shaded habitats. While its primary mode of reproduction is vegetative, successful sexual reproduction may occur despite several limiting factors.Item CHROMIUM OXIDATION AND REDUCTION BY HYDROGEN PEROXIDE IN DIVERSE SOILS AND SIMPLE AQUEOUS SYSTEMS(1999) Rock, Melanie Louise; Helz, George R.; James, Bruce R.; Chemistry; Environmental Science & Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Hydrogen peroxide is being tested for in situ remediation of buried contaminants - either as a direct chemical oxidant in Fenton-type reactions or as a source of oxidizing equivalents in bioremediation. How it affects a common co-contaminant, Cr, is explored here in four chemically diverse high-Cr soils. Soils contaminated with high levels of soluble Cr(VI) from ore processing and soils containing high levels of recently reduced Cr(III) from electroplating waste showed marked increases in chromate after single applications of J-25 mM peroxide. Cr(VI) in the leachates exceeded the drinking water standard (2μM) by 1-3 orders of magnitude. Soluble Cr(III), in the form of dissolved organic complexes, contributed to the likelihood of Cr(III) oxidation. Anaerobic soil conditions at a tannery site prevented oxidation of Cr(III). Naturally occurring Cr in serpentine soil also resisted oxidation. Ambient soluble Cr(VI) in a contaminated aquifer disappeared from peroxide leachates below pH 5, then reappeared as peroxide levels declined. In solutions prepared under environmentally relevant conditions, aged 280 μM Cr(III) treated with 100 μM H2O2 showed increases in Cr(VI) over weeks with maximum oxidation rates achieved in solutions prepared with 2:1 and 4:1 OH^-:Cr. Although Cr(III) speciation differs in fresh and aged aqueous systems, a similar mechanism involving the pre-equilibrium step: Cr(OH)/ + OH- .,. Cr(OH)/ may account for Cr(III) oxidation in both systems. Under alkaline conditions, H2O2 enhanced the oxidative dissolution of Crn(OH)3n^0. The formation of peroxochromium compounds in the presence of H2O2 and Cr(VI) may account for the disappearance and reappearance of Cr(VI) in H2O2 treated soils; as does the possible formation and subsequent reoxidation of Crm\(OH)3n-2^2+ oligomers. Mobilization of hazardous Cr(VI) must be considered in plans to use H2O2 for remediation of chemically complex wastes. Once Cr(III) is oxidized to Cr(VI) by H2O2 it may persist long after applied H2O2 treatments have disappeared. Further, hexavalent Cr will behave as a catalyst toward H20 2 in soils, enhancing its oxidative capacity while helping to dissipate high levels of applied H2O2.Item A COMPARATIVE HYDROLOGIC ANALYSIS OF SURFACE MINED AND FORESTED WATERSHEDS IN WESTERN MARYLAND(2002) Negley, Timothy Lee; Eshleman, Keith N.; Environmental Science & Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)This thesis presents the results of a hydrologic analysis conducted as part of a larger, multi-faceted, collaborative effort to study ecosystem function of a watershed subjected to surface mining and reclamation in the Appalachian Region of the United States. The primary goal of this study was to determine whether a small watershed subjected to surface mine reclamation practices (MAT 1) displayed a stormflow response to rain events that was different from those displayed by a young second-growth forested watershed (NEFl). A secondary goal was to investigate whether intensive surface mining in the Georges Creek basin has altered stormflow response at a larger river basin scale when compared to a similar, but predominantly forested basin (Savage River). At the small watersheds, MATl produced greater a) runoff coefficients (2.5x); b) total runoff (3x); and c) peak runoff rates (2x) compared to NEFl. Total rainfall explained 63% of the variation in total runoff at MAT I compared to only 21 % of the variation in total runoff at NEF I. Regardless of a recent 13% increase in surface mine reclamation in the Georges Creek basin, little difference in stormflow response was observed for 15 storms analyzed across the two larger basins. Georges Creek on average responded 3 hr more quickly than Savage River, However the hydrological response characteristics of the two basins were similar. In addition, hydrological response characteristics for Georges Creek and Savage River remained relatively stable over time. Further research is needed to address inabilities to scale responses observed at the small watersheds.Item Preliminary Stock Assessment of The Chesapeake Bay Blue Crab Population(1989) Knotts, Karen Sue; Rothschild, Brian J.; Environmental Science & Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)A preliminary stock assessment using data from a commercial fishery survey was completed. The maximum average attainable size (Linf) was found to be 174.25 mm (6.9 in) for males, and 171.7 mm (6.8 in) for females. The von Bertalanffy growth coefficient (K) was determined to be 0.83 for males and 0.57 for females. Yield-per-recruit analysis indicated that a significant amount of yield-per-recruit is lost if males are fished before reaching approximately 145 mm (5.7 inches). Results for females show that the size at first capture should be approximately 124 mm (5 inches), after which the yield-per-recruit gained by waiting is minimal. The nature of the recruitment-stock relationship could not be characterized in this study; however, results indicate that a relationship does exist. A comparison of early and late season catch curves indicated surplus production of biomass in the 1987 pot fishery. The potential use of change in sex ratios estimators for stock assessment is discussed.Item Soils with Spodic Characteristics on the Eastern Shore of Maryland(1990) Condron, Margaret Anne; Rabenhorst, Martin C.; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)A seasonally fluctuating water table may be an important factor in the formation of spodic horizons in sandy, quartzose sediments on the Lower Eastern Shore of Maryland. This study was conducted to examine spodic horizon formation and expression along two topohydrosequences. After a reconnaissance study, two research sites were chosen in the Pocomoke State Forest in Worcester County, Maryland. The soils were classified according to Soil Taxonomy as siliceous, mesic, Typic Quartzipsamments, Aquic Haplorthods, and Aerie and Typic Haplaquods. The spodic horizons were thickest (26-204cm) in the wettest positions. Total organic carbon, pyrophosphateextractable carbon, and extractable aluminum were greatest in the spodic horizons, and there was little extractable iron in the Haplaquods. There was less structural aluminum and potassium in the surface horizons than in the lower horizons. This suggests that feldspar weathering in the surface horizons provides a source of aluminum for the spodic horizon formation. Quantitative estimates of pedogenesis showed net gains of extractable aluminum, total (organic) carbon, and pyrophosphate carbon in the lower landscape positions. The seasonally fluctuating water table appears to influence the movement of soluble organic aluminum complexes through the soil downslope, as well as within the pedon from the surface to subjacent horizons.Item AN INVESTIGATION OF THE RELATIONSHIP BETWEEN THE LEVEL OF ANTIBIOTIC RESISTANCE OF ESCHERICHIA COLI IN NONTIDAL WETLANDS AND COMMON WETLAND HEALTH FACTORS(2008-05-25) Agarwal, Neil; Ahearn, Sean; Dudziak, Erik; Khan, Sehba; Marcin, Daniel; Shofnos, Matthew; Skoda, Emily; Venkatachari, Padmasini; Vocke, Robert; Tilley, DavidThis report investigated the prevalence of antibiotic resistance among Escherichia coli in the water of 13 non-tidal mitigation wetlands in Maryland, and its relation to land use and wetland health. At each site, land use, surface and sub-surface water samples, soil samples, and vegetation cover were collected. From the water samples, individual colonies of E. coli were isolated and tested, using the disc diffusion method, for resistance to the antibiotics ampicillin, ciprofloxacin, erythromycin, sulfisoxazole, and tetracycline. According to soils, vegetation and water quality improvement criteria the wetlands function like healthy wetlands. The wetlands' E. coli exhibit resistance to all of the antibiotics tested, except for ciprofloxacin. There were statistically significant relationships found between land use and antibiotic resistance, vegetation, soil and water chemistry. Surprisingly, E. coli in wetlands with smaller stocks of carbon and nitrogen in their soil exhibited more resistance to tetracycline, possibly indicating that soil quality plays an important role in fostering or fighting antibiotic resistance. The work demonstrates that antibiotic resistance is present in Maryland's wetlands, but that its spread could be subdued by healthy wetlands.Item Advanced imaging and data mining technologies for medical and food safety applications(2009) Jiang, Lu; Tao, Yang; Biological Resources Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As one of the most fast-developing research areas, biological imaging and image analysis receive more and more attentions, and have been already widely applied in many scientific fields including medical diagnosis and food safety inspection. To further investigate such a very interesting area, this research is mainly focused on advanced imaging and pattern recognition technologies in both medical and food safety applications, which include 1) noise reduction of ultra-low-dose multi-slice helical CT imaging for early lung cancer screening, and 2) automated discrimination between walnut shell and meat under hyperspectral florescence imaging. In the medical imaging and diagnosis area, because X-ray computed tomography (CT) has been applied to screen large populations for early lung cancer detection during the last decade, more and more attentions have been paid to studying low-dose, even ultra-low-dose X-ray CTs. However, reducing CT radiation exposure inevitably increases the noise level in the sinogram, thereby degrading the quality of reconstructed CT images. Thus, how to reduce the noise levels in the low-dose CT images becomes a meaningful topic. In this research, a nonparametric smoothing method with block based thin plate smoothing splines and the roughness penalty was introduced to restore the ultra-low-dose helical CT raw data, which was acquired under 120 kVp / 10 mAs protocol. The objective thorax image quality evaluation was first conducted to assess the image quality and noise level of proposed method. A web-based subjective evaluation system was also built for the total of 23 radiologists to compare proposed approach with traditional sinogram restoration method. Both objective and subjective evaluation studies showed the effectiveness of proposed thin-plate based nonparametric regression method in sinogram restoration of multi-slice helical ultra-low-dose CT. In food quality inspection area, automated discrimination between walnut shell and meat has become an imperative task in the walnut postharvest processing industry in the U.S. This research developed two hyperspectral fluorescence imaging based approaches, which were capable of differentiating walnut small shell fragments from meat. Firstly, a principal component analysis (PCA) and Gaussian mixture model (PCA-GMM)-based Bayesian classification method was introduced. PCA was used to extract features, and then the optimal number of components in PCA was selected by a cross-validation technique. The PCA-GMM-based Bayesian classifier was further applied to differentiate the walnut shell and meat according to the class-conditional probability and the prior estimated by the Gaussian mixture model. The experimental results showed the effectiveness of this PCA-GMM approach, and an overall 98.2% recognition rate was achieved. Secondly, Gaussian-kernel based Support Vector Machine (SVM) was presented for the walnut shell and meat discrimination in the hyperspectral florescence imagery. SVM was applied to seek an optimal low to high dimensional mapping such that the nonlinear separable input data in the original input data space became separable on the mapped high dimensional space, and hence fulfilled the classification between walnut shell and meat. An overall recognition rate of 98.7% was achieved by this method. Although the hyperspectral fluorescence imaging is capable of differentiating between walnut shell and meat, one persistent problem is how to deal with huge amount of data acquired by the hyperspectral imaging system, and hence improve the efficiency of application system. To solve this problem, an Independent Component Analysis with k-Nearest Neighbor Classifier (ICA-kNN) approach was presented in this research to reduce the data redundancy while not sacrifice the classification performance too much. An overall 90.6% detection rate was achieved given 10 optimal wavelengths, which constituted only 13% of the total acquired hyperspectral image data. In order to further evaluate the proposed method, the classification results of the ICA-kNN approach were also compared to the kNN classifier method alone. The experimental results showed that the ICA-kNN method with fewer wavelengths had the same performance as the kNN classifier alone using information from all 79 wavelengths. This demonstrated the effectiveness of the proposed ICA-kNN method for the hyperspectral band selection in the walnut shell and meat classification.Item Evaluation of the effects of wetland restoration design on hydraulic residence time and nutrient retention(2009) Strano, Stephen; Felton, Gary K; Biological Resources Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Hydraulic residence time (HRT) is a critical factor that can be integrated into wetland restoration designs to promote nutrient retention, but HRT in the context of wetlands with storm-driven hydrology is not well understood. A model for nutrient retention optimization based on HRT was evaluated using three indicators of HRT and nutrient stocks in above-ground plant biomass. Results indicated that a commonly used indicator of HRT, the ratio of wetland to watershed area, may be insufficient, while nominal HRT provided an overestimate for wetlands receiving storm runoff. While there was little relationship between total nitrogen and HRT, results suggested that HRT may explain some variation in total phosphorus. Results also indicated that the studied wetland restorations were not designed to provide sufficient HRT to promote the retention of dissolved nutrients, and that staged outlets could be used to provide significant HRT's for a range of storm events.